Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (3 Viewers)

[Thumpalumpacus]

If it was set incorrectly it would explode when the cockpit door was slammed shut.

Sound like a great front-line aircraft to me.

 

[pbehn]

Your comment about the effect of a hit by the 37 is, again overly simplistic. You are correct in that a hit would ruin anyone's day but compared to the 20mm Hispano II

37mm rof 150 rpm mv 2,000ft/min
20mm rof 600 rpm mv 2,700ft/min

You are far more likely to be hit by multiple 20mm rounds which would also ruin anyone's day

Generally between 1 and 3 hits from a 20 mm cannon would take down an S/E aircraft, a Typhoon was firing 16 times as many shells per second.

 

[Crimea_River]

I like beer.

 

[fubar57]

 

[P-39 Expert]

Actually, the USAAF had moved to six .50s in the -51, eight in the -47, four .50s and a cannon in the -38, and the Navy in 1943 had standardized on the F6F's six .50s, so I'm seeing a bit of underselling here on your part. Oh, and the F4U1 had six .50s as well.

If you're pulling guns, armor, and the goddamned radio to get climb or maneuverability, your plane probably ain't cutting the mustard.

The P-47, P-38, F6F and F4F all came out before the P-51B/C, FM2 or F8F, so the services were moving to 4 50calMGs. The P-51D went to six, but by then air superiority over Europe had been won and it didn't really matter. If a plane is too heavy it aint cutting the mustard as you say. If you can lighten it then it can cut the mustard.

 

[Crimea_River]

 

[P-39 Expert]

No one would deny that there was a disappointment in the altitude performance of the Typhoon, but your statement Only reason the Typhoon was a fighter bomber was because it couldn't do interception at high altitude is as ever, far too simplistic.

The RAF had the Spitfire as an interceptor which was always very effective at altitude. What the Typhoon had in its favour was the following:-
a) an exceptional low level performance at low / medium altitude Reaching approx 400mph at 8,800ft 415mph at 20,000ft, a lot faster than a Spitfire
b) The capability of carrying very heavy payload of up to 2,000lb plus of course 4 x 20mm
c) It was well armoured with pilot eventually sitting in almost a bath of armour

Lets look at those parameters on the P39
a) P39N 398 mph at 9,700ft 389 mph at 16,100ft Both are very quick and its likely that the inevitable differences you get in mass production would make them very similar.
b) I am not sure what the GA capability of the P39 is but it seems to be in the area of 500lb of bombs which isn't even close to the capability of the Typhoon
c) Again I haven't seen anything that shows the P39 as having anything remotely close to the armour protection of the Typhoon
Note the P39Q seems to have a worse performance

The RAF lacks a GA aircraft and the Typhoon had all the right attributes, that's why it was the RAF's premier GA aircraft.

Your comment about the effect of a hit by the 37 is, again overly simplistic. You are correct in that a hit would ruin anyone's day but compared to the 20mm Hispano II

37mm rof 150 rpm mv 2,000ft/min
20mm rof 600 rpm mv 2,700ft/min

You are far more likely to be hit by multiple 20mm rounds which would also ruin anyone's day

wwiiaircraftperformance.org shows the Typhoon to make 375mph at 10000ft and 395mph at 20000ft and climbed at 2000fpm at 20000ft. The P-39N was at least as fast and outclimbed the Typhoon by 600fpm at all altitudes.

 

[pbehn]

It was most certainly the British who changed the requirements, it was their production contract and it was amended more than once. They signed the initial contract without armor plate and added it during the construction process as they realized it was needed.

Yes, these things happen in a world war, the Hurricane had armour and self sealing tanks installed along with all sorts of radio gizmos and 4 cannon. It was a world war not a Reno handicap race.

 

[FLYBOYJ]

The 20mm cannon was just an example to illustrate that Bell was able to balance the P-39/400 with either cannon in the nose even though one was 140lbs lighter than the other. Surely you know that, right?

I do know that, but you continue to try to use issues like this to justify most of your arguments. And again, if you take weight out of the nose by installing a lighter cannon you're making matters worse! If you want, I'll do a weight balance calculation with a 20 mm cannon and remove the gear box armor.

This tells me that the P-400 probably had ballast in the nose along with that (drumroll) gear box armor!

BTW - You "balance" on a see-saw, you "balance" on a tight rope, you get an airplane in "Center of Gravity Range" or C/G.

 

[FLYBOYJ]

re the IFF in early P-39s in the PTO.

The first IFF used by the US was the UK IFF Mk I 'Pipsqueak' or RC-96-A in US terms, which was basically just an intermittent broadcast circuit for the radio transmitter set. This sent out a predetermined pulse of abut 14 seconds, switched back to normal radio operation for a predetermined time, then sent out the 14 sec pulse again, etc. The frequency of the pulse was the same as the radar detecting it.

I know this was used with the SCR-522 VHF set (BC-608-A) fitted in the P-39 in the PTO. I have seen diagrams and weight lists.

I think it was also used in some of the early airframes fitted with the SCR-274 sets (BC-608-A & BC-616). I have seen weight lists but not any diagrams of the fit.

I have also read accounts about the US using 'Pipsqueak' in the PTO but I do not remember where or exactly why, other than to help not get shot down by US or Australian friendlies.

There are diagrams that show "radios" in the tail and behind the pilot. If you have any other data or equipment/ weight lists that you could share, we'd really appreciate it!

 

[Glider]

wwiiaircraftperformance.org shows the Typhoon to make 375mph at 10000ft and 395mph at 20000ft and climbed at 2000fpm at 20000ft. The P-39N was at least as fast and outclimbed the Typhoon by 600fpm at all altitudes.

From the web site you quoted

August 1943.
Cleaning up.
The remaining cleaning up modifications are now on the production machine. (I think we can agree that this was the standard production version of the Typhoon for the war in Europe, post invasion)

These are(a) Exhaust shrouds.(b) Whip aerial(c) Sliding hood.
Tests at Gloster on a repaired aircraft with a whip aerial and sliding hood fitted have given the following level speeds corrected on the basis of A. & A.E.E. Res.170.
M.S. M.P.A 398 m.p.h. at 8,800ft F.S. M.P.A 417 m.p.h. at 20,500ft.

Note - I also notice that you don't disagree with my comments on the Payload carried by the Typhoon, its much better armour and general firepower.

 

[Thumpalumpacus]

The P-47, P-38, F6F and F4F all came out before the P-51B/C, FM2 or F8F, so the services were moving to 4 50calMGs. The P-51D went to six, but by then air superiority over Europe had been won and it didn't really matter. If a plane is too heavy it aint cutting the mustard as you say. If you can lighten it then it can cut the mustard.

You're doing some fine cherry-picking here. I'm not big on interrupting things, but by 1944 only the F8F was moving forward with 4x.50s

How many P-51B/C/Ds served in ETO, compared to any model of P-39?

How many P-47C/Ds or P-38s served in ETO and SoWesPac compared to the P-39?

If only you'd held Hap Arnold's chair! If only your insight had rescued the Allies from the folly of building the P-47, P-38, and P-51 in mass numbers. Gosh, we might have won the war in the air.

 

[Shortround6]

Only reason the Typhoon was a fighter bomber was because it couldn't do interception at high altitude. P-39 was a beast at low altitude, go to wwiiaircraftperformance and compare them with the Typhoon. And one hit from a 37mm cannon will definitely ruin your day no matter what you are flying.

Quite right, a hit assuming there is one will ruin your day. '
How good is your day if you are hit by 16 20mm shells?
Difference in the rate of fire of the 37mm and four 20mm Hispano guns.
The Hispano guns, being higher velocity, are easier to hit with.

P-39s could NOT do interceptions at high altitude either.

I am comparing the P-39M (nov 1942) to the Typhoon (Nov 1942) not seeing the Beast.
P-39M does 345mph at 2750ft using 57in of Map and 322mph using military power. Typhoon does 349.5 at 2000ft and 357.5 at 4,000ft. using 7lbs of boost.

 

[Shortround6]

As to the four .50 cal thing.

The need for six guns waxed and waned. Most gun histories don't give dates or at least not good ones. It was hard to figure out what the "planners" intended or hoped for a year or more down the road.

The US .50 jumped from 600rpm (free firing with short belts and no G load) to about 800rpm in late 1940. The Americans very quickly started multiple projects to increase the rate of fire to 1200rpm. At least three different companies and some of them ran simultaneous projects and some ran sequential projects. The records show something like 15 (?) different model numbers. A batch of several thousand (10,000?) were built using a "T" number in late 1944/45 before it was standardized as the M3. The F8F may never have gotten the fast firing guns but the intent to use them cannot be ruled out.
The programs suffered numerous failures in trying to meet the US desired standards of rate of fire, parts broken or jams per 1000 rounds fired and gun life (not barrel life).
At any given moment a future fighter may have been intended to use four fast firing guns only to be let down by the gun development program/s.

 

[Greg Boeser]

One cannon and two .50s ain't really a suitable armament suite for 1942-43 in a plane that is struggling to keep up on performance parameters as well. Add in short range and limited altitude performance, meh.

Tell that to Messerschmitt, Yakovlev, Lavochkin, and company

 

[Greg Boeser]

No it couldn't land on a carrier, but then neither could the F4U-1. And range was equivalent to either the Navy fighters.

F4U-1s were landing on carriers from their inception. VF-17 was to be the fighter complement on board USS Bunker Hill (CV-17) but was pulled off when the carrier reached Hawaii. They flew from land bases because the Navy wanted to keep their fleet air wings standardized and Grumman was cranking out a lot of F6Fs. The RN was flying Corsairs from jeep carriers long before the USN decided to upgrade the fleet air wings in the face of kamikaze attacks. The F4U's speed advantage being a key consideration. VF-17 did a one off during the Navy's attack on Rabaul, 11 Nov 1943. Flying from their land base they flew CAP for the fleet, landed on the carriers to refuel and then flew another CAP before returning to their base. During this mission they engaged an enemy air attack as well as shot down enemy snoopers.

 

[Thumpalumpacus]

Tell that to Messerschmitt, Yakovlev, Lavochkin, and company

Tell that to Sakai & co.

 

[Shortround6]

Tell that to Messerschmitt, Yakovlev, Lavochkin, and company

You have to look at the guns,

The Russian 12.7mm MG would fire at 800rpm or close to it when synchronized. The US .50 in the early planes was under 500 rpm in the cowl. Later ones might have been better? but not near 800rpm. Some authors say it neve got over 600rpm for a cowl gun.
The Germans, once they got the MG 131 were firing at 900rpm per barrel. being electric primed it only lost about 10% of it's rate of fire when synchronized. A lot less powerful but you had around 50% higher rate of fire to make up for it.

Similar story for the 20mm guns through the prop. Not as powerful as the Hispano but higher rates of fire.
The American 37mm was both low velocity and ssslllooooooww firing. Not a good combination for air to air gunnery.

150rpm and 610m/s velocity.

German Mg 151/20 fired close to 700rpm and velocity was 700-785M/s depending on projectile. Gun in the 109 was free firing, guns in the wing roots of the 190 were synchronized.

Russian 20mm ShVAk cannon fired at 700-800rpm and had a velocity of 750-790 m/s.

a plane flying at 300mph is going to move 176ft between shots from the US cannon.

I would also note the US combination has the worst mismatch by far of trajectory and time of flight of the three examples. You can pretty much kiss off any hope of long range gunnery hitting with both guns at the same time. This suited the Russians who preferred to get in close (perhaps because in many of their planes the guns sights were rather rudimentary?)

 

[Greg Boeser]

Well, if you dumped the .50s for pulse cannon I think the P-39 would be unstoppable.

 

[Shortround6]

This plane was armed (or planned to be) with two .50s and two 37mm cannon.
Part of the nose was supposed to tilt so both types of guns would hit in the same place at various ranges.